Toilets, Sinks, Showers, Tubs and Disposals - Offset toilet flange

I have a new toilet which sits on the old flange in a concrete floor 4 inches from the wall. I want it to be against the wall. I know there are offset flanges but I have questions:
1) can the flange just be placed on top of the pipe or will I have to chip out cement
2) can a flange move things back this far or only 2 inches
3) Can I use 2 2 inch flanges to move things back 4 inches

I looked through 12 pages of posts and didn't see a similar question, but I have the same problem. I am remodeling a bathroom on a slab. It is roughed out for a shower, but the shower drain is too close to the toilet and too far from the wall. I plan to build a small platform to "adjust" the drain for the shower without having to break up the concrete. I also need to move the toilet over a few inches. I bought a skinnier toilet to help reduce the amount I have to move it, but still think 2" more would make a big difference. I'd like to avoid breaking up the concrete to accomplish my goals.

You would have to chip out at least <i>some</i> concrete to set an offset flange. I'm not too crazy about offset flanges in the first place, and they can't be 'doubled' to get more offset. I'm not even sure you can get 2", but perhaps they do make one that offsets that much.

Breaking concrete can be pretty quick, with the right tools.

It looks like I'll be trying something new.